The modified Bessel functions of the second kind K_m can be represented by: 
I tried to calculate this integral with Mathematica Version 12:
f[t_] := Exp[-x*Cosh[t]]*Cosh[m*t];
Integrate[f[t], {t, 0, Infinity}]
Unfortunately Mathematica does give no result by solving the integral above. Can someone explain me, how to solve this integral with Mathematica. Thank you for your help in advance. Ruediger
